The 1,570 cc all-alloy twin-cam is a strong, long-lived engine — but its cooling system is the weak point, and neglect here does real damage. This is the check that separates a healthy car from an expensive one.
What neglect does
Coolant left too long without fresh corrosion inhibitor turns aggressive. In an all-alloy engine that means two things at once: it erodes and weakens the alloy castings, and it silts up the radiator. Together they cause overheating and, in the worst case, blown head gaskets. Because the damage is internal, a car can look fine and still be quietly cooking itself.
The proper cure — and the shortcut that isn't
When a head gasket has gone or the engine has overheated, a head skim alone is not enough. The radiator should be recored or replaced to clear the silting, and where the castings have been eaten away, skilled welding may be needed to build the strength back in. Treat a car that has "just had the head off" with informed questions about what else was done.
What to check
- Look at the coolant condition as well as the level — clean and correctly inhibited, not brown, oily or thick.
- Watch the temperature on a test drive: drive it hard, then leave it idling. A healthy car holds its temperature; one that climbs and keeps climbing at idle is telling you something.
- Check for coolant leaks, weeping hoses and a furred or leaking radiator.
Keeping it healthy
The prevention is simple and cheap: use the correct coolant with a proper corrosion inhibitor for alloy engines, renew it on schedule rather than endlessly topping up, and keep the radiator and hoses in good order. On an alloy twin-cam, coolant discipline is engine-preservation, not just maintenance.